// Copyright (c) 2015-2019 Amanieu d'Antras and DGuco(杜国超).All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

namespace stagefuture
{
namespace detail
{

// Set of events that an task_wait_event can hold
enum wait_type
{
    // The task that is being waited on has completed
        task_finished = 1,

    // A task is available to execute from the scheduler
        task_available = 2
};

// OS-supported event object which can be used to wait for either a task to
// finish or for the scheduler to have more work for the current thread.
class task_wait_event
{
    std::mutex m;
    std::condition_variable c;
    int event_mask;

public:
    task_wait_event()
        : event_mask(0)
    {}

    // Wait for an event to occur. Returns the event(s) that occurred. This also
    // clears any pending events afterwards.
    int wait()
    {
        std::unique_lock<std::mutex> lock(m);
        while (event_mask == 0)
            c.wait(lock);
        int result = event_mask;
        event_mask = 0;
        return result != 0;
    }

    // Check if a specific event is ready
    bool try_wait(int event)
    {
        std::unique_lock<std::mutex> lock(m);
        int result = event_mask & event;
        event_mask &= ~event;
        return result != 0;
    }

    // Signal an event and wake up a sleeping thread
    void signal(int event)
    {
        std::lock_guard<std::mutex> lock(m);
        event_mask |= event;
        c.notify_one();
    }
};

} // namespace detail
} // namespace stagefuture
